Association between Dental Caries, Obesity and Salivary Alpha Amylase in Adolescent Girls of Babol City, Iran-2017

Statement of the Problem: Adolescents are at risk of obesity and caries due to various factors such as diet and poor health habits; these factors may affect their body mass index (BMI) and salivary components. Therefore, it is necessary to assess these factors and their relationship in this age group. Purpose: This study aimed to evaluate the association between decayed missing filled teeth index (DMFT), salivary alpha amylase (sAA) level and age-specific BMI in adolescent girls. Materials and Method: A cross-sectional study was conducted on 81 females aged 13-15 years in 3 groups of BMI percentiles; “normal”, “at risk for overweight” and “overweight” (n=27). DMFT was calculated and unstimulated saliva samples were collected. The sAA level was measured with a spectrophotometer. Data were analyzed using Kolmogorov-Smir-nov test, Kruskal- Wallis and Spearman correlation tests using SPSS (version 23) at p< 0.05. Results: The concentration of sAA and mean DMFT were estimated 1326.56±4.73 U/L and 2.77±2.36, respectively. There was no significant difference in sAA level and mean DMFT among BMI groups. A positive and significant correlation was found between sAA and DMFT in overweight group (r 0.46, p= 0.014). Conclusion: Within the limitation of this study, higher levels of sAA may be considered as an indicator for dental caries in overweight adolescent girls.


Introduction
Adolescence is defined as a critical developmental period of life experienced from the ages of 10 to 24 years [1]. Unhealthy dietary habits including consumption of industrial foods high in fat, sodium, carbohydrate, and low fiber intake along with low physical activity can affect general heath of adolescents [2]. Also, the puberty brings stress, emotional imbalance and rebellion for teenagers that influence their lifestyle [3]. Paying attention to body health of adolescents is a momentous responsibility to prevent serious chronic diseases that may establish later in their life [4].
The two most prevalent problems among teenagers are dental caries and obesity [4][5]. According to a World Health Organization (WHO) report on 2018 [5], the worldwide prevalence of obesity for children and adolescents has risen more than ten folds in the last 4 decades. The result of a systematic review conducted by BMI is between 85th and 95th percentiles, and they are known as clinically overweight if the BMI exceeds the 95th percentile [8]. Unfortunately, there is a lack of systematic data on the prevalence of dental caries in Iranian adolescents. Pakpour et al. [9] and Yazdani et al. [10] in two separate cross-sectional studies reported DMFT of 2.6 and 2.1, respectively for Iranian teenagers which is higher than the standard (DMFT=1) determined by the WHO [11].
Obesity and dental caries are both multifactorial phenomena which are influenced by both genetic and environmental factors [6,12]. Despite the correlation established between obesity and tooth decay in adults, the evidence confirming this association in adolescents is controversial [13][14][15]. It is generally agreed that an etiologic factor common to both tooth decay and obesity is high carbohydrate intake especially in adolescent years [14]. One of the salivary components related to dental caries is salivary alpha amylase (sAA) [16]. This enzyme consists at least 50% of salivary proteins and plays a role in starch hydrolysis [17]. It is demonstrated that this enzyme facilitates the microbial adhesion to enamel surface and acid production [16]. The level and activity of sAA can be changed under specific situations including stress, anxiety, exercise and circadian rhythms. The higher basal sAA has been found in adolescents with more advanced pubertal development [18]. However, the association between sAA activity and BMI is controversial [19][20][21]. Al dossari et al. [17] showed a reverse correlation between sAA and BMI in overweight and obese adults. In contrast, Mennella et al. [19] indicated a higher sAA activity in overweight individuals. Because of the known importance of alpha amylase and the controversies found in various article and also, due to the lack of an article exclusively on the effect of this enzyme during adolescence, the present study aimed to assess the association between DMFT, sAA and BMI in a selected population of Iranian adolescent girls.

Materials and Method
This cross-sectional study was carried out on female  [18], the selected participants were grouped in 85> BMI>5 (normal weight) 85> BMI> 95(at risk for overweight), and BMI>95(over weight). Oral examination was done by a trained dental student using WHO criteria for caries detection and then the DMFT was recorded [22]. The teeth that were extracted or repaired due to trauma or extracted because of orthodontic treatment were not included in the DMFT calculation. The unstimulated saliva samples were collected at the morning, at least 2 hours after eating. The students were kept seated and relaxed to allow the saliva to be accumulated in the mouth for 5 minutes. Then, the saliva samples were poured in the containers and were dispatched to the laboratory in the flasks including ice cubes. The amount of sAA was measured using the special kit (Zist Shimi Co., Iran) and spectrophotometric method (Unico, USA). Data were analyzed using Kolmogorov-Smirnov test, Kruskal Wallis test and Spearman correlation coefficient using SPSS (version 23) and p< 0.05 was considered statistically significant. The study variables are listed in Table 1. The details were shown in Table 2  According to Kruskal Wallis test, no significant difference was found among sAA level and DMFT of different BMI percentiles (Table 3).

Discussion
Considering the results of the current study, no significant difference was found between sAA levels in overweight adolescents compared to those who were in "normal" and "at risk for overweight" groups. Although the effect of sAA gene on the risk of obesity has been confirmed, its mechanism remains unclear and there are conflicting results on the association between sAA and obesity [19][20][21]. Rukh et al. [23] revealed no association between sAA gene copy number and BMI in adults but they indicated that increasing the sAA gene copy number in people with low and high starch intake has a reverse and direct correlation with BMI, respectively. there were not enough underweight samples in the study area. In contrast, Ghasempour et al. [15] showed that caries activity increased by weight in 3-to 6-year-old children. Furthermore, Sakeenabi et al. [31] found a positive association between caries incidence and overweight in 6-to 12-year-old children. In another study, Willershausen et al. [32] investigated the association of overweight and dental caries in 6-to11-year-old children and concluded that the prevalence of primary and permanent tooth decay was related to overweight. The authors believed that these findings were related to their dietary habit and high amount of carbohydrate intake.
Overall, this discrepancy can be explained regarding difference in age range of study population and sample size and characteristics. The present study was conducted on adolescent girls in permanent dentition while the mentioned studies were done on children in primary or mixed dentitions. Whereas dental caries and obesity are multifactorial in nature, contradictory results were predictable and many confounding factors should be taken into account. Moreover, the results should be interpreted carefully because these studies usually are cross sectional; it means BMI might change by time while its effect on teeth could yet remain.
In the present study, a positive correlation was found between sAA level and DMFT only in overweight group. This finding may be related to the level of starch intake by the overweight subjects. As mentioned, excessive consumption of starch by people with higher levels of sAA puts them at risk of obesity [23]. On the other hand, high carbohydrate intake is related to dental caries [13] and food habits must be considered for proper interpretation of these findings. Since the current study did not consider the dietary habits, the above findings cannot be interpreted definitively.
The available data concerning the association between dental caries and sAA are limited and inconsistent [33][34][35][36]. Mojarad et al. [33] in a matched casecontrol study assessed the sAA level in 3-to 6-year-old children with and without tooth decay. They found a considerable relationship between low level of sAA and susceptibility to dental caries and declared that although, the study groups were matched for oral hygiene and dietary habits, the other salivary components such as immunoglobulins with possible synergistic or antagonistic effects on sAA were not assessed. Finally, they could not firmly establish a proper sequence between dental caries and sAA. Ahmadi-Motamayel et al. [34] and Sitaru et al. [35] revealed a relationship between sAA and dental caries but Farias et al. [36] did not confirm such a relationship. Ahmadi-Motamayel et al. [34] investigated the relationship between sAA and tooth decay on caries-active and caries-free adolescents with limiting the confounding variables including stress, exercise, smoking, and caffeine intake because of their strong impact on sAA concentration. They concluded that high amount of sAA increases the susceptibility to dental caries by hydrolysis of starch and facilitating the acid production by cariogenic bacteria. Sitaru et al. [35] conducted a research on 10-to 14- Additionally, matching the confounding factors such as oral hygiene, food habits, salivary immunoglobulins, stress level and so on, are suggested for future studies.

Conclusion
The concentration of sAA and DMFT were not different among overweight and non-overweight adolescent girls.
There was a positive correlation between sAA level and DMFT in overweight adolescent girls.